1. Field of the Invention
The present invention relates to printed circuit board mounting fixtures and, more particularly, to a PC board card housing and guide for facilitating insertion and removal of the card from a mounting connector and preventing the electrical contacts on the card from shorting out against other cards during that process.
2. History of Related Art
Early designs of electrical circuits included a plurality of discrete components which were electrically connected to one another by means of wires. A major advance occurred with the advent of printed circuit boards whereby components were mounted on rigid insulative substrates and electrically interconnected with one another by a pattern of conductive leads formed on the upper and lower surfaces of the substrate by a photoresist and etch process. Each so-called printed circuit card is electrically connected with circuitry on other cards is by rows of electrically conductive plated fingers spaced from one another along both sides of one edge of the printed circuit card. The card edge containing the conductive fingers is received into a card edge connector in which each plated finger removably engages a connector contact for electrical connection to other circuitry on other printed circuit cards.
Rows of card edge connectors are conventionally mounted adjacent to one another in rows on a, so-called, motherboard with the printed circuit cards being received into each of the card edge connectors. The connectors mounted on the motherboard have their contacts interconnected with one another by means of similar conductive wiring placed on the surfaces of the motherboard. The use of the printed circuit card edge connector concept in the design of electronic equipment, such as digital computers, allows cards to be added and removed for repair, upgrade, and/or changes in functionality in the circuitry.
Originally, a rule of practice in the maintenance of electrical circuitry, such as computer hardware, was that of always turning the power to the motherboard off before cards were added or removed from the card edge connectors. Such a policy was for both reasons of safety of the technician as well as to avoid injury to the circuitry on the cards.
Recent innovations in this area have addressed the desirability to insert and remove printed circuit cards from electrical equipment, such as computer hardware, when the computer is electrically connected and operational, i.e. "hot." In these cases, it is now possible to disconnect the power from only the connector of the card to be inserted and removed while allowing the adjacent cards to remain "hot." In these situations, and because of the close spacing between adjacent card edge connectors on a motherboard, it is possible to inadvertently allow the plated fingers along the edge of the printed circuit card to touch an adjacent card which is hot and thereby produce a short circuit and create a hazard to the technician and the circuitry on both of the PC cards. Data stored within memory elements of the circuitry may be irretrievably lost when this occurs. It is thus important to minimize the exposure of adjacent PC boards during the insertion or removal process.
It would be an advantage therefore to provide a printed circuit (PC) board assembly that would eliminate the possibility of an electrical short while not interfering with the normal functional insertion and removal of the PC board assembly. The present invention provides such an assembly by providing a PC board card guide for securement to the PC board. The card guide is comprised of at least one pair of isolation arms in the form of a channel that is adapted to receive a wide variety of PC board sizes. The channel arms are configured to extend outwardly on opposite sides of the PC board forming a nonconductive bumper to eliminate accidental engagement between adjacent PC boards.